Choke valves for use in the downhole environment of oil wells are well known. However it is difficult to design and construct choke valves that fit within the restricted available space, that operate using limited power and that have long operational lifetimes. These choke valves must control the flow rate from high pressure oil reservoirs in the presence of fluids that contain abrasive particulate material such as sand, possibly in significant concentrations.
Also known in the prior art is Jackson, U.S. Pat. No. 6,860,330, issued Mar. 1, 2005, which is said to disclose a choke valve assembly for controlling the flow of fluid through a production tubing. The valve assembly includes a housing having a plurality of axially aligned apertures and a ported sleeve disposed in the housing. The ported sleeve has a plurality of rows of fluid ports. Each row of ports has at least one port in selective fluid communication with a respective aperture. In the full open position, each aperture is in fluid communication with a port from each row. To choke the flow, the ported sleeve is rotated relative to the housing to reduce the number of ports in fluid communication with the housing. To close the valve, axial force is applied to move the ported sleeve axially relative to the housing.
There is a need for improved valves for control of flow in oil production.